Mechanism to handle events in a machine with isolated execution

ABSTRACT

A platform and method for secure handling of events in an isolated environment. A processor executing in isolated execution “IsoX” mode may leak data when an event occurs as a result of the event being handled in a traditional manner based on the exception vector. By defining a class of events to be handled in IsoX mode, and switching between a normal memory map and an IsoX memory map dynamically in response to receipt of an event of the class, data security may be maintained in the face of such events.

CLAIM TO PRIORITY

This application is a divisional application of co-pending U.S. Ser. No.09/672,368, filed Sep. 28, 2000, entitled, “Mechanism To Handle EventsIn A Machine With Isolated Execution”.

BACKGROUND

(1) Field of the Invention

The invention relates to platform security. More specifically, theinvention relates to handling asynchronous events in a secure manner.

(2) Background

Data security is an ongoing concern in our increasingly data-drivensociety. To that end, multimode platforms have been developed to supportboth normal execution and isolated execution. A section of memory isallocated for use only in the isolated execution mode. Encryption andauthentication are used any time isolated data is moved into anon-isolated section of memory. In this manner, data used and maintainedin isolated execution mode is not security compromised. However, duringisolated execution that data may reside, for example, in the processorcache in an unencrypted form. Certain asynchronous events may cause thatdata to be accessible in a normal execution mode thereby compromisingthe data security.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

FIG. 1A is a diagram illustrating an embodiment of the logical operatingarchitecture for the IsoX™ architecture of the platform.

FIG. 1B is an illustrative diagram showing the accessibility of variouselements in the operating system and the processor according to oneembodiment of the invention.

FIG. 1C is a first block diagram of an illustrative embodiment of aplatform utilizing the present invention.

FIG. 2 is a block diagram of a memory map selection unit of oneembodiment of the invention.

FIG. 3 is a flow diagram of operation response to an asynchronous eventin one embodiment of the invention.

DETAILED DESCRIPTION

The present invention relates to a platform and method for securehandling of asynchronous events in an isolated environment. A processorexecuting in isolated execution “IsoX” mode may leak data when anasynchronous event occurs as a result of the event being handled in atraditional manner based on the exception vector. By defining a class ofasynchronous events to be handled in IsoX mode, and switching between anormal memory map and an IsoX memory map dynamically in response toreceipt of an asynchronous event of the class, data security may bemaintained in the face of such events.

In the following description, certain terminology is used to discussfeatures of the present invention. For example, a “platform” includescomponents that perform different functions on stored information.Examples of a platform include, but are not limited or restricted to acomputer (e.g., desktop, a laptop, a hand-held, a server, a workstation,etc.), desktop office equipment (e.g., printer, scanner, a facsimilemachine, etc.), a wireless telephone handset, a television set-top box,and the like. Examples of a “component” include hardware (e.g., anintegrated circuit, etc.) and/or one or more software modules. A“software module” is code that, when executed, performs a certainfunction. This code may include an operating system, an application, anapplet or even a nub being a series of code instructions, possibly asubset of code from an applet. A “link” is broadly defined as one ormore information-carrying mediums (e.g., electrical wire, optical fiber,cable, bus, or air in combination with wireless signaling technology) toestablish a communication pathway. This pathway is deemed “protected”when it is virtually impossible to modify information routed over thepathway without detection.

In addition, the term “information” is defined as one or more bits ofdata, address, and/or control and a “segment” is one or more bytes ofinformation. A “message” is a grouping of information, possiblypacketized information. “Keying material” includes any informationneeded for a specific cryptographic algorithm such as a DigitalSignature Algorithm. A “one-way function” is a function, mathematical orotherwise, that converts information from a variable-length to afixed-length (referred to as a “hash value” or “digest”). The term“one-way” indicates that there does not readily exist an inversefunction to recover any discernible portion of the original informationfrom the fixed-length hash value. Examples of a hash function includeMD5 provided by RSA Data Security of Redwood City, Calif., or SecureHash Algorithm (SHA-1) as specified in a 1995 publication Secure HashStandard FIPS 180-1 entitled “Federal Information Processing StandardsPublication” (Apr. 17, 1995).

I. Architecture Overview

A platform utilizing an embodiment of the invention may be configuredwith an isolated execution (IsoX™) architecture. The IsoX™ architectureincludes logical and physical definitions of hardware and softwarecomponents that interact directly or indirectly with an operating systemof the platform. Herein, the operating system and a processor of theplatform may have several levels of hierarchy, referred to as rings,which correspond to various operational modes. A “ring” is a logicaldivision of hardware and software components that are designed toperform dedicated tasks within the platform. The division is typicallybased on the degree or level of privilege, namely the ability to makechanges to the platform. For example, a ring-0 is the innermost ring,being at the highest level of the hierarchy. Ring-0 encompasses the mostcritical, privileged components. Ring-3 is the outermost ring, being atthe lowest level of the hierarchy. Ring-3 typically encompasses userlevel applications, which are normally given the lowest level ofprivilege. Ring-1 and ring-2 represent the intermediate rings withdecreasing levels of privilege.

FIG. 1A is a diagram illustrating an embodiment of a logical operatingarchitecture 50 of the IsoX™ architecture. The logical operatingarchitecture 50 is an abstraction of the components of the operatingsystem and processor. The logical operating architecture 50 includesring-0 10, ring-1 20, ring-2 30, ring-3 40, and a processor nub loader52. Each ring in the logical operating architecture 50 can operate ineither (i) a normal execution mode or (ii) an IsoX mode. The processornub loader 52 is an instance of a processor executive (PE) handler.

Ring-0 10 includes two portions: a normal execution Ring-0 11 and anisolated execution Ring-0 15. The normal execution Ring-0 11 includessoftware modules that are critical for the operating system, usuallyreferred to as the “kernel”. These software modules include a primaryoperating system 12 (e.g., kernel), software drivers 13, and hardwaredrivers 14. The isolated execution Ring-0 15 includes an operatingsystem (OS) nub 16 and a processor nub 18 as described below. The OS nub16 and the processor nub 18 are instances of an OS executive (OSE) andprocessor executive (PE), respectively. The OSE and the PE are part ofexecutive entities that operate in a protected environment associatedwith the isolated area 70 and the IsoX mode. The processor nub loader 52is a bootstrap loader code that is responsible for loading the processornub 18 from the processor or chipset into an isolated area as explainedbelow.

Similarly, ring-1 20, ring-2 30, and ring-3 40 include normal executionring-1 21, ring-2 31, ring-3 41, and isolated execution ring-1 25,ring-2 35, and ring-3 45, respectively. In particular, normal executionring-3 includes N applications 42 ₁-42 _(N) and isolated executionring-3 includes M applets 46 ₁-46 _(M) (where “N” and “M” are positivewhole numbers).

One concept of the IsoX™ architecture is the creation of an isolatedregion in the system memory, which is protected by components of theplatform (e.g., the processor and chipset). This isolated region,referred to herein as an “isolated area,” may also be in cache memorythat is protected by a translation look aside (TLB) access check. Accessto this isolated area is permitted only from a front side bus (FSB) ofthe processor, using special bus cycles (referred to as “isolated readand write cycles”) issued by the processor executing in IsoX mode.

The IsoX mode is initialized using a privileged instruction in theprocessor, combined with the processor nub loader 52. The processor nubloader 52 verifies and loads a ring-0 nub software module (e.g.,processor nub 18) into the isolated area. For security purposes, theprocessor nub loader 52 is non-modifiable, tamper-resistant andnon-substitutable. In one embodiment, the processor nub loader 52 isimplemented in read only memory (ROM).

One task of the processor nub 18 is to verify and load the ring-0 OS nub16 into the isolated area. The OS nub 16 provides links to services inthe primary operating system 12 (e.g., the unprotected segments of theoperating system), provides page management within the isolated area,and has the responsibility for loading ring-3 application modules 45,including applets 46 ₁ to 46 _(M), into protected pages allocated in theisolated area. The OS nub 16 may also support paging of data between theisolated area and ordinary (e.g., non-isolated) memory. If so, then theOS nub 16 is also responsible for the integrity and confidentiality ofthe isolated area pages before evicting the page to the ordinary memory,and for checking the page contents upon restoration of the page.

Referring now to FIG. 1B, a diagram of the illustrative elementsassociated with the operating system 10 and the processor for oneembodiment of the invention is shown. For illustration purposes, onlyelements of ring-0 10 and ring-3 40 are shown. The various elements inthe logical operating architecture 50 access an accessible physicalmemory 60 according to their ring hierarchy and the execution mode.

The accessible physical memory 60 includes an isolated area 70 and anon-isolated area 80. The isolated area 70 includes applet pages 72 andnub pages 74. The non-isolated area 80 includes application pages 82 andoperating system pages 84. The isolated area 70 is accessible only tocomponents of the operating system and processor operating in the IsoXmode. The non-isolated area 80 is accessible to all elements of thering-0 operating system and processor.

The normal execution ring-0 11 including the primary OS 12, the softwaredrivers 13, and the hardware drivers 14, can access both the OS pages 84and the application pages 82. The normal execution ring-3, includingapplications 42 ₁ to 42 _(N), can access only to the application pages82. Both the normal execution ring-0 11 and ring-3 41, however, cannotaccess the isolated area 70.

The isolated execution ring-0 15, including the OS nub 16 and theprocessor nub 18, can access to both of the isolated area 70, includingthe applet pages 72 and the nub pages 74, and the non-isolated area 80,including the application pages 82 and the OS pages 84. The isolatedexecution ring-3 45, including applets 46 ₁ to 46 _(M), can access onlyto the application pages 82 and the applet pages 72. The applets 46 ₁ to46 _(M) reside in the isolated area 70.

Referring to FIG. 1C, a block diagram of an illustrative embodiment of aplatform utilizing the present invention is shown. In this embodiment,platform 100 comprises a processor 110, a chipset 120, a system memory140 and peripheral components (e.g., tokens 180/182 coupled to a tokenlink 185 and/or a token reader 190) in communication with each other. Itis further contemplated that the platform 100 may contain optionalcomponents such as a non-volatile memory (e.g., flash) 160 andadditional peripheral components. Examples of these additionalperipheral components include, but are not limited or restricted to amass storage device 170 and one or more input/output (I/O) devices 175.For clarity, the specific links for these peripheral components (e.g., aPeripheral Component Interconnect (PCI) bus, an accelerated graphicsport (AGP) bus, an Industry Standard Architecture (ISA) bus, a UniversalSerial Bus (USB) bus, wireless transmitter/receiver combinations, etc.)are not shown.

In general, the processor 110 represents a central processing unit ofany type of architecture, such as complex instruction set computers(CISC), reduced instruction set computers (RISC), very long instructionword (VLIW), or hybrid architecture. In one embodiment, the processor110 includes multiple logical processors. A “logical processor,”sometimes referred to as a thread, is a functional unit within aphysical processor having an architectural state and physical resourcesallocated according to a specific partitioning functionality. Thus, amulti-threaded processor includes multiple logical processors. Theprocessor 110 is compatible with the Intel Architecture (IA) processor,such as a PENTIUM® series, the IA-32™ and IA-64™. It will be appreciatedby those skilled in the art that the basic description and operation ofthe processor 110 applies to either a single processor platform or amulti-processor platform.

The processor 110 may operate in a normal execution mode or an IsoXmode. In particular, an isolated execution circuit 115 provides amechanism to allow the processor 110 to operate in an IsoX mode. Theisolated execution circuit 115 provides hardware and software supportfor the IsoX mode. This support includes configuration for isolatedexecution, definition of the isolated area, definition (e.g., decodingand execution) of isolated instructions, generation of isolated accessbus cycles, and generation of isolated mode interrupts. In oneembodiment, a memory map selection unit 112 exists within the processor110 to select dynamically between alternative memory maps that may beemployed by the processor 110.

As shown in FIG. 1C, a host link 116 is a front side bus that providesinterface signals to allow the processor 110 to communicate with otherprocessors or the chipset 120. In addition to normal mode, the host link116 supports an isolated access link mode with corresponding interfacesignals for isolated read and write cycles when the processor 110 isconfigured in the IsoX mode. The isolated access link mode is assertedon memory accesses initiated while the processor 110 is in the IsoX modeif the physical address falls within the isolated area address range.The isolated access link mode is also asserted on instruction pre-fetchand cache write-back cycles if the address is within the isolated areaaddress range. The processor 110 responds to snoop cycles to a cachedaddress within the isolated area address range if the isolated accessbus cycle is asserted.

Herein, the chipset 120 includes a memory control hub (MCH) 130 and aninput/output control hub (ICH) 150 described below. The MCH 130 and theICH 150 may be integrated into the same chip or placed in separate chipsoperating together.

With respect to the chipset 120, a MCH 130 provides control andconfiguration of memory and input/output devices such as the systemmemory 140 and the ICH 150. The MCH 130 provides interface circuits torecognize and service attestation cycles and/or isolated memory read andwrite cycles. In addition, the MCH 130 has memory range registers (e.g.,base and length registers) to represent the isolated area in the systemmemory 140. Once configured, the MCH 130 aborts any access to theisolated area when the isolated access link mode is not asserted.

The system memory 140 stores code and data. The system memory 140 istypically implemented with dynamic random access memory (DRAM) or staticrandom access memory (SRAM). The system memory 140 includes theaccessible physical memory 60 (shown in FIG. 1B). The accessiblephysical memory 60 includes the isolated area 70 and the non-isolatedarea 80 as shown in FIG. 1B. The isolated area 70 is the memory areathat is defined by the processor 110 when operating in the IsoX mode.Access to the isolated area 70 is restricted and is enforced by theprocessor 110 and/or the chipset 120 that integrates the isolated areafunctionality. The non-isolated area 80 includes a loaded operatingsystem (OS). The loaded OS 142 is the portion of the operating systemthat is typically loaded from the mass storage device 170 via some bootcode in a boot storage such as a boot read only memory (ROM). Of course,the system memory 140 may also include other programs or data which arenot shown.

As shown in FIG. 1C, the ICH 150 supports isolated execution in additionto traditional I/O functions. In this embodiment, the ICH 150 comprisesat least the processor nub loader 52 (shown in FIG. 1A), ahardware-protected memory 152, an isolated execution logical processingmanager 154, and a token link interface 158. For clarity, only one ICH150 is shown although platform 100 may be implemented with multipleICHs. When there are multiple ICHs, a designated ICH is selected tocontrol the isolated area configuration and status. This selection maybe performed by an external strapping pin. As is known by one skilled inthe art, other methods of selecting can be used.

The processor nub loader 52, as shown in FIGS. 1A and 1C, includes aprocessor nub loader code and its hash value (or digest). After beinginvoked by execution of an appropriated isolated instruction (e.g.,ISO_INIT) by the processor 110, the processor nub loader 52 istransferred to the isolated area 70. Thereafter, the processor nubloader 52 copies the processor nub 18 from the non-volatile memory 160into the isolated area 70, verifies and places a representation of theprocessor nub 18 (e.g., a hash value) into the protected memory 152.Herein, the protected memory 152 is implemented as a memory array withsingle write, multiple read capability. This non-modifiable capabilityis controlled by logic or is part of the inherent nature of the memoryitself. For example, as shown, the protected memory 152 may include aplurality of single write, multiple read registers.

As shown in FIG. 1C, the protected memory 152 is configured to supportan audit log 156. An “audit log” 156 is information concerning theoperating environment of the platform 100; namely, a listing of datathat represents what information has been successfully loaded into thesystem memory 140 after power-on of the platform 100. For example, therepresentative data may be hash values of each software module loadedinto the system memory 140. These software modules may include theprocessor nub 18, the OS nub 16, and/or any other critical softwaremodules (e.g., ring-0 modules) loaded into the isolated area 70. Thus,the audit log 156 can act as a fingerprint that identifies informationloaded into the platform (e.g., the ring-0 code controlling the isolatedexecution configuration and operation), and is used to attest or provethe state of the current isolated execution.

In another embodiment, both the protected memory 152 and unprotectedmemory (e.g., a memory array in the non-isolated area 80 of the systemmemory 140 of FIG. 1C) may collectively provide a protected audit log156. The audit log 156 and information concerning the state of the auditlog 156 (e.g., a total hash value for the representative data within theaudit log 156) are stored in the protected memory 152.

Referring still to FIG. 1C, the non-volatile memory 160 storesnon-volatile information. Typically, the non-volatile memory 160 isimplemented in flash memory. The non-volatile memory 160 includes theprocessor nub 18 as described above. Additionally, the processor nub 18may also provide application programming interface (API) abstractions tolow-level security services provided by other hardware and may bedistributed by the original equipment manufacturer (OEM) or operatingsystem vendor (OSV) via a boot disk.

The mass storage device 170 stores archive information such as code(e.g., processor nub 18), programs, files, data, applications (e.g.,applications 42 ₁-42 _(N)), applets (e.g., applets 46 ₁ to 46 _(M)) andoperating systems. The mass storage device 170 may include a compactdisk (CD) ROM 172, a hard drive 176, or any other magnetic or opticstorage devices. The mass storage device 170 also provides a mechanismto read platform-readable media. When implemented in software, theelements of the present invention are stored in a processor readablemedium. The “processor readable medium” may include any medium that canstore or transfer information. Examples of the processor readable mediuminclude an electronic circuit, a semiconductor memory device, a readonly memory (ROM), a flash memory, an erasable programmable ROM (EPROM),a fiber optic medium, a radio frequency (RF) link, and any platformreadable media such as a floppy diskette, a CD-ROM, an optical disk, ahard disk, etc.

In communication with the platform 100, I/O devices 175 includestationary or portable user input devices, each of which performs one ormore I/O functions. Examples of a stationary user input device include akeyboard, a keypad, a mouse, a trackball, a touch pad, and a stylus.Examples of a portable user input device include a handset, beeper,hand-held (e.g., personal digital assistant) or any wireless device.

FIG. 2 is a block diagram of a memory map selection unit of oneembodiment of the invention. A set of current control registers 200defines the memory map currently employed by the processor. This set ofcontrol registers includes a current interrupt descriptor table (IDT)register 234, a current global descriptor table (GDT) register 236, anda page table map base address register 238 (also referred to herein ascontrol register 3, abbreviated CR3). By changing the values in thesecurrent control registers 200, the memory map used by the processor ischanged. Thus, for example, by changing current CR3 238, a differentpage table map comes into use.

A set of control registers 202 from which the current control registers200 may be loaded are also retained with the processor. The set ofcontrol registers 202 includes two subsets, an IsoX subset, and a normalsubset, including IsoX IDT 204, IsoX GDT 206 and IsoX CR3 208 and IDT218, GDT 216 and CR3 218, respectively. A plurality of selection units,such as multiplexers 220, 222, 224, are used to select between the firstand second subset of the set of control registers 202. The selectionsignal is provided by selection signal generation unit 230, whichemploys the IsoX mode bit in conjunction with an event vector togenerate the selection signal to the multiplexers 220, 222 and 224. Inone embodiment, the events to be handled in IsoX mode are stored in alookup table (LUT), and the event vector is used as an index to the LUTto identify if the event should be handled in an IsoX mode. Byappropriately populating the LUT the OS nub can ensure that any event(whether synchronous or asynchronous) is handled in isolated executionmode if desired. It is also within the scope and contemplation of theinvention for the OS nub to dynamically modify the LUT from time totime.

In this manner, the current memory map corresponding to IDT 234, GDT216, and CR3 238, can be dynamically changed responsive to the receiptof an event. Accordingly, it is possible to ensure that an asynchronousevent, such as a machine check, which might otherwise cause a dataleakage, is always handled in isolated mode using an appropriate memorymap. Thus, on receipt of a machine check, selection signal generationunit 230 asserts a selection signal to select control registers 204, 206and 208 to have their contents loaded into current IDT register 234,current GDT register 236 and current CR3 register 238, respectively. Theexception vector may then be dispatched and will be handled using theIsoX memory map. Other types of events such as non-maskable interrupts(NMI) or clock interrupts may be, at the discretion of the OS nubhandled in isolated execution mode, even where data leakage is not aconcern. For example, in the context of the clock interrupt requiringthat it be handled by the isolated environment avoids denial of serviceconditions in the OS nub.

The IsoX mode bit is also used to control writes to the first subset ofcontrol registers in control register set 202. By requiring isolatedexecution mode for any changes to the IsoX subset 204, 206 and 208,software attack by corrupting the memory mapping for asynchronous eventhandling is prevented.

FIG. 3 is a flow diagram of operation response to an asynchronous eventin one embodiment of the invention. At function block 302, anasynchronous event is received. A determination is made at functionalblock 304 if the event is of a class to be handled in IsoX mode. Thisdetermination may be implicit, such as by applying the vector to a logicblock or explicit such as where the vector is used to index into a LUT.If the event is not of the class, a determination is made at decisionblock 306 if the platform is currently in IsoX mode. If it is, thememory map selection unit is activated to reload the current controlregisters selecting the normal memory map at functional block 308.

If at decision block 304 the event is of a class to be handled in anIsoX mode, a determination is made at decision 310 whether the platformis in IsoX mode. If it is not in IsoX mode, the selection signalgeneration unit causes the memory map selection unit to load the currentcontrol registers with the IsoX memory map at functional block 312.After the appropriate memory map is loaded, or is determined to alreadybe loaded, the vector is dispatched and the asynchronous event ishandled at function block 314.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes can be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

1. An apparatus comprising: a cache memory; a processor coupled with thecache memory, the processor comprising: logic to cause the processor toenter a first mode in response to a first instruction, wherein the firstmode is to be indicated by a first mode bit, and wherein the first modecorresponds to a different security level than a normal mode of theprocessor, and wherein in the first mode a first program is to controlaccess to a secure portion of the cache memory using a translationlook-aside buffer; a flash interface to communicate with a flash memory;a wireless interface to communicate with a wireless device; a universalserial bus (USB) interface to communicate with a USB device; and akeypad interface to communicate with a keypad.
 2. The apparatus of claim1, wherein in the first mode the first program is further to restrictaccess to a special-purpose control register.
 3. The apparatus of claim2, wherein the special-purpose control register is a virtual memorymanagement descriptor.
 4. The apparatus of claim 2, wherein thespecial-purpose control register is an interrupt vector tabledescriptor.
 5. An apparatus comprising: a cache memory; a processorcoupled with the cache memory, the processor comprising: logic to causea first class of events to be handled by a secure event handlingresource and a second class of events to be handled by a normal eventhandling resource, wherein the secure event handling resourcecorresponds to a protected memory region and wherein the normal eventhandling resource corresponds to an unprotected memory region. a flashinterface to communicate with a flash memory; a wireless interface tocommunicate with a wireless device; a universal serial bus (USB)interface to communicate with a USB device; and a keypad interface tocommunicate with a keypad.
 6. The apparatus of claim 5, wherein thefirst class of events comprises at least one of a machine checkexception event, a clock event, and a hardware interrupt event.
 7. Theapparatus of claim 5, wherein the secure event handling resourcecomprises logic to access a secure interrupt vector table.